1. Field of the Invention
The present teachings relate to ink jet printers and, more particularly, relate to roll to roll ink jet printers having a print head using light emitting diodes (LEDs).
2. Background
Historically, roll to roll inkjet printers have been used to create prints that are viewed at long distances, such as for paper or vinyl billboard prints. Such prints are not typically required to be of high quality, and the technology used for many years was solvent inks.
More recently, UV ink technology has been applied to roll to roll inkjet printers, which has allowed the printing of a greater range of substrates and at improved print quality. For example, FIG. 1 shows a first exemplary Roll to Roll printer 10 having UV curing 24. In the exemplary printer 10 seen in FIG. 1, a substrate 14 is moved 18, such as over an inlet roller 16, a plurality of rollers 12, over a cooling mechanism 26, and an outlet roller 28. A print carriage 20 comprising one or more inkjet heads 22 applies ink to the substrate 14 as it passes over the rollers 12. The ink on the substrate 14 is then cured by one or more UV curing lamps 24, which may be located over a cooling mechanism 26.
While such UV printers have provided adequate quality for a limited range of printing applications, UV light sources 24 commonly heat the both substrate 14 and neighboring surfaces of the printing mechanisms to as much as 150 to 200 degrees Fahrenheit (F), which may commonly cause problems for any of placement accuracy of the UV curable ink drops 22, or accurate positioning or movement of substrates 14. For example, heat from UV light sources 24 readily builds up though substrates 14 and rollers, which can cause many substrates, especially thin or temperature sensitive substrates, to stretch or wrinkle, making it difficult for the substrate to print-head gap to remain accurate or constant. Such heat build up typically restricts the types of substrates 14 that can be used in UV printers.
Printers having UV light sources 24 may provide cooling of the substrate, such as with a chilled platen or other cooling mechanism 26, wherein cooling water may typically be circulated to chill a metal platen in contact with the substrate 14. As well, some UV printers have cooling water pass through tubes that resist UV absorption, located between the UV light sources 24 and the substrate 14, to reduce heat that would otherwise reach the substrate.
There is an ongoing need for higher quality prints, with higher resolution, which has been driven by the desire to produce a wide variety of printing products, such as but not limited to any of point of purchase (POP) items, labels, and packaging, where close up viewing is a requirement. Increases in printer throughput are a continuing requirement that is driven by customer costs and competition.
In recent years, this has driven the cost of printer design higher, as more heads have often been required, such as to increase print speed and/or to increase printer tolerances. As well, chilled platens have been used, such as with thermoelectric devices, or the region near UV lamps has been chilled, such as by running cooling water in front of lamps, such as to provide motion quality for the expanded range of substrates, e.g. thinner and/or temperature sensitive substrates, and the requirement for improved drop placement accuracy.
While such UV printers have provided adequate quality for some printing applications, UV light sources 24 commonly heat the both substrate and the neighboring surface of the drum to as much as 150 to 200 degrees Fahrenheit (F). For mercury vapor printing systems, substrates are commonly heated to as much as 150 to 220 degrees F., depending upon such factors as lamp type, power output and speed setting. Even with chilling and a low power setting, mercury vapor printing systems commonly heat substrates to over 100 degrees F.
It would be advantageous to provide a printing system that can produce a wide variety of printed matter with high resolution that can be viewed close up, such as for point of purchase (POP) items, labels, and packaging. The development of such a printing system would constitute a major technological advance.
As well, it would be advantageous to provide such a printing system that can produce a wide variety of printed matter on a wide variety of substrates, such as for thin and/or temperature sensitive substrates. The development of such a printing system would constitute a further technological advance.
In addition, it would be advantageous to provide such a printing system that can produce a wide variety of printed matter on a wide variety of substrates, without the necessity of platen chilling. The development of such a printing system would constitute a further technological advance.
Some recent flat printers having flat platens have used LED curing for applied ink. FIG. 2 shows a second exemplary inkjet printer 30 having LED curing 38 for a flat platen 32. For example, substrate media 40 may be placed or positioned between a print head assembly 34 and a platen 32, wherein the printer 30 comprises one or more heads 36, and one or more LED light sources 38.
While such flat format printers 30 have begun to implement LED curing, such flat printer configurations are often expensive and may only provide a limited range to printed output.
It would therefore be advantageous to provide a printing system that can cost-effectively produce a wider variety of printed matter across a wider range of substrates. The development of such a printing system would constitute a further technological advance.